Silica-glass electric appliance.



U ITED s'rATEs PATENToFnIon] HE Y ANDREW KENT, or" BOUN'DS GREEN, AN HAEDLD GEoEo LAcEL .OF

FINCHLEY, ENGLAND, As'sIGNoEsro sI oA SYNDICATE LIMITED, OF Lo DoN,

ENGLAND.

sILIcA oLAss ELECTRIC APPLIANCE.-

No Drawing;

Specification of Letters Patent. Patented 25, 1913. 'Application filed November 21, 1912. Serial No. 732,697.

To (ill whom it may concern.

.Be it known-that we, HENRY ANDREW KENT, a subject of the King of Great Britain and Ireland, of The Poplars, Maidstone' Road, Bounds Green, in the county of Middlesex, England, and HAROLD GEORGE LAGELL, a subject of the King of Great Britain and Ireland, of Ardoch, Nether street, Finchley, in the county of Middlesex, England, have invented new and useful Improvements in Silica-Glass Electric Appliances, of which the following is a specifica.-'

tion.

It has been proposed to employ leadingin Wires of either molybdenum or tungsten for evacuated electrical devices with which it was customary to employ platinum leading-in wires.

The object of this invention is to overcome difliculties which have been experienced in combining leading-in wires with articles -made of silica glass.

It is to be noted that the present invention does not relate to devices made of glass with which it has been customary to employ platinum leading-in wires but solely to devices made of silica glass, to which latter platinum leading-in wires have not been applied because the fusing point of silica glass is so high that platinum would be is not suitable for 'use for leading-in wires for silica glass articles as the electric conductivity of tungsten is so low as to require wires of too great a diameter.

4 After numerous trials and experiments the present inventors have found that, as far as they have been able to ascertain molybdenum is the only metal which fulfils the requisite conditions as a very small sectlonal area of that metal will carry a large current while the said metal will withstand the high temperature employed in manufacturing articles of silica glass. It is necessary that the molybdemum while being applied should, as far as possible, be protected from oxidation and for that purpose the molybdenum wire of small cross section should be inserted in a small orifice 1n the silica glass so that but a very small amount of air can come in contact with the metal while the heated silica glass is closed around it, or the operation of embedding the molybdenum wire in the silica glass is carrled on in a vacuum, or in a non-oxidizing atmosphere. Thejoint between the molybdenum and the silica glass can be made so that it will constitute a complete seal against the passage. of mercury, or other llquid,

although it is not essential that it should 

